Method For Packaging Flash Memory Cards

ABSTRACT

A method for packaging flash memory cards is provided, including the steps of forming a shell base, placing a circuit substrate inside the shell base with electric contact parts exposed, and using insert molding to form a monolithic shell to enclose the circuit substrate. The electric contacts parts of the circuit substrate remain exposed. The method provides a stronger structure for memory cards, and better water-proof against humidity leakage.

FIELD OF THE INVENTION

The present invention generally relates to mini flash memory cards, andmore specifically to a packaging method applicable to various types ofmini flash memory cards.

BACKGROUND OF THE INVENTION

The current types of the flash memory cards include compact flash (CF)card, smart media card (SMC), multimedia card (MMC), secure digital (SD)card, and memory stick (MS) card. The xD-Picture card, being a newdesign, is a high speed read/write flash storage media that is low inpower consumption and the smallest in size. The conventional packagingmethods for this type of structure usually employ the gluing forfixation.

FIG. 1 shows an exploded view of the structure of a conventional miniSD, including a cover housing shell 11, a circuit substrate 2, and abottom housing shell 13. Cover housing shell 11 and bottom housing shell13 are manufactured by inject molding to form the required shape.Circuit substrate 2 includes the already packaged chips and relatedelectric connections. During assembly, circuit substrate 2 is placed inbottom housing shell 13, and cover housing shell 11 is placed on top ofbottom housing shell 13 to cover circuit substrate 2. A supersonicthermal pressing method is used to glue cover housing shell 11 andbottom housing shell 13 together to seal in circuit substrate 2, withonly the electric contact parts 21 on one end of circuit substrate 2exposed. This type of structure has the drawback of weakness structurebecause cover housing shell 11, circuit substrate 2 and bottom housingshell 13 are not seamlessly fixed together. The potential gap betweenthem will weaken the structure strength. In addition, cover housingshell 11 is easily disintegrated from bottom housing shell 13 afterrepetitive uses, and it is easy for water/humidity to leak in to causedamage to the circuit. All these drawbacks shorten the lifespan of theflash memory cards. It is imperative to develop a more effectivepackaging method to improve the conventional techniques.

SUMMARY OF THE INVENTION

The present invention has been made to overcome the aforementioneddrawback of conventional packaging methods. The primary object of thepresent invention is to provide a packaging method that is robust andwater-proof. The method of the present invention includes the use ofinsert molding to bury a circuit substrate inside a protective shell sothat the protective shell tightly houses the circuit substrate inside.The method provides a structure that is strong and gap-free so thathumidity leakage is prevented.

Another object of the present invention is to provide a packaging methodthat is applicable to a variety of flash memory card types, includingmajor categories, such as, compact flash (CF) card, smart media card(SMC), multimedia card (MMC), secure digital (SD) card, and memory stick(MS) card, and the new xD-Picture card, a high speed read/write flashstorage media that is low in power consumption and the smallest in size.

To achieve the above objects, the present invention includes a methodincluding the steps of forming a shell base, placing an electricallyconnected circuit substrate inside the shell base, using insert moldingto form a shell enclosing the circuit substrate with only the electriccontact parts of the circuit substrate exposed.

In comparison with the conventional packaging methods, the presentinvention provides a flash memory cards packaging method that providesbetter protection against water leakage and stress on the structurecaused by repetitive uses.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become better understood from a careful readingof a detailed description provided herein below with appropriatereference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be understood in more detail by reading thesubsequent detailed description in conjunction with the examples andreferences made to the accompanying drawings, wherein:

FIG. 1 shows an exploded view of the structure of a conventional mini SDmemory card;

FIG. 2 shows a flowchart of the present invention;

FIG. 3 shows a three-dimensional view of the shell base and the circuitsubstrate of an mini SD memory card when applying the present invention;and

FIG. 4 shows a three-dimensional view of the final mini SD memory cardmanufacture by the method of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 2 shows a flowchart of the flash memory card packaging method ofthe present invention. As shown in FIG. 2, the present inventionincludes the following steps. Step 31 is to manufacture a shell base.Step 32 is to place a circuit substrate inside the shell base with theelectric contact parts on the circuit substrate surface uncovered. Step33 is to place the shell base inside a mold and use insert molding toflow the molding material over the top and the circumference of thecircuit substrate and form a monolithic shell with the shell base sothat the monolithic shell covers the top surface, bottom surface and thecircumference of the circuit substrate with only the electric contactparts uncovered, i.e., exposed.

The packaging method is applicable to a variety of flash memory cardtypes, including major categories, such as, compact flash (CF) card,smart media card (SMC), multimedia card (MMC), secure digital (SD) card,and memory stick (MS) card, and the new xD-Picture card, a high speedread/write flash storage media that is low in power consumption and thesmallest in size.

For better clarity, the following embodiment uses a mini SD card as anexample for explanation. As shown in FIG. 3, a shell base 4 ismanufactured by inject molding to have the shape that meets the standardspecification, while having a thinner thickness. The top surface ofshell base 4 includes a concave space 41 with a shape matching the shapeof a circuit substrate 5 so that circuit substrate 5 fits inside concavespace 41. Circuit substrate 5 is a printed circuit board (PCB) that isalready electrically connected. The top of circuit substrate 5 includesa plurality of electric contact parts 51, commonly known as goldfingers, for providing electric contact with the device that the flashmemory card plugs in. As shown in FIG. 4, when shell base 4 with circuitsubstrate 5 is placed inside a mold, the aforementioned step 32 isperformed to flow the molding material over the top and thecircumference of circuit substrate 5 and form a monolithic shell 6 withshell base 4. Monolithic shell 6 encloses circuit substrate 5, and thethickness of monolithic shell 6 meets the specifications of standardmemory cards.

Shell base 4 and monolithic shell 6 are both made of material containingacrylnitrie-butadience-styrene copolymer (ABS) or poly carbonate (PC).Shell base 4 is infused with the material used in insert molding to formmonolithic shell 6 so that the final structure is sufficiently strong toavoid disintegration. As there is no gap exists in monolithic shell 6and circuit substrate 5, the water/humidity leakage is prevented, andthe lifespan of the packaged flash memory card is improved.

Although the embodiment shows that shell base 4 has the shape matching amini SD card, and concave space 41 has the shape matching circuitsubstrate 5, the packaging method of the present invention is notlimited to this type of memory cards. When the method of the presentinvention is applied to other types of memory cards, the shape of shellbase 4 and the shape of concave space 41 can be changed to match thetype of the memory cards.

In summary, present invention uses insert molding to form a monolithicshell with the original shell base so that the circuit substrate istightly sealed inside the final monolithic structure. The finalmonolithic structure of the flash memory card is stronger, providesbetter water-proof against humidity leakage.

Although the present invention has been described with reference to thepreferred embodiments, it will be understood that the invention is notlimited to the details described thereof. Various substitutions andmodifications have been suggested in the foregoing description, andothers will occur to those of ordinary skill in the art. Therefore, allsuch substitutions and modifications are intended to be embraced withinthe scope of the invention as defined in the appended claims.

1. A method for packaging flash memory cards, comprising the steps of:forming a shell base; placing a circuit substrate inside said shellbase, with a plurality of electric contact parts on said circuitsubstrate surface uncovered; placing said shell base inside a mold andusing insert molding to form a monolithic shell with said shell base sothat the monolithic shell enclosing the top surface, bottom surface andthe circumference of said circuit substrate with only said electriccontact parts exposed.
 2. The method as claimed in claim 1, wherein saidinsert molding step is to flow a molding material over the top and thecircumference of said circuit substrate to infuse with said shell baseto form said monolithic shell enclosing said circuit substrate.
 3. TheThe method as claimed in claim 1, wherein the top surface of said shellbase comprises a concave space for housing said circuit substrate. 4.The method as claimed in claim 1, wherein said circuit substrate is aprinted circuit board (PCB) with complete electric connections.
 5. Themethod as claimed in claim 1, wherein said method is applied to an SDcard or mini SD card.
 6. The method as claimed in claim 1, wherein saidmethod is applied to an MMC card or MMC plus card.
 7. The method asclaimed in claim 1, wherein said method is applied to an SM card.
 8. Themethod as claimed in claim 1, wherein said method is applied to an MScard.
 9. The method as claimed in claim 1, wherein said method isapplied to an xD-Picture card.
 10. The method as claimed in claim 1,wherein said method is applied to a CF card.